As a monitor mounted in a cab of a hydraulic excavator and the like, a monitor including a liquid crystal display has been typically known (see Patent Literature 1). In such a monitor, circuit substrates such as a power supply substrate and a control substrate are disposed on a back of the liquid crystal display. The circuit substrates are housed in a rear case made of aluminium. When a downsized monitor is used in a working vehicle such as a hydraulic excavator, a vision of an operator of the working vehicle is not hindered during operation while watching a working surface and the like.
Since a temperature inside the rear case is increased by heat generated from a liquid crystal display and a circuit substrate, a vent for ventilation is provided on a side wall of the rear case and a plurality of fins are provided on an outer surface of the rear case, so that the heat inside the rear case can be efficiently radiated outside.
Moreover, a plurality of connectors attached to the circuit substrate inside the rear case are exposed from a back of the rear case. To the connectors, a power cable from a battery mounted in the hydraulic excavator and a communication cable from a controller for controlling the entire hydraulic excavator are connected.
When a history of failure having occurred in the hydraulic excavator is stored in a storage within the monitor, a serviceman occasionally removes the communication cable, connects a communication cable, which is connected to a personal computer prepared for failure analysis, to the connector of the monitor, and downloads necessary data from the storage to the personal computer. In a hydraulic excavator having CAN (Controller Area Network), the data within the monitor is occasionally read via CAN without removing the communication cable connected to the monitor. In the occurrence of a phenomenon that the data cannot be downloaded, an operation for checking presence or absence of a connection failure and the like of the connector by inserting and removing the connector is performed. In the case of malfunction of the monitor, an operation of removing the communication cable from the monitor is naturally required.
The monitor disclosed in Patent Literature 1 is mounted in a relatively large-sized hydraulic excavator. In a small-sized hydraulic excavator provided with a cab or a canopy, a small-sized monitor is mounted. In the small-sized monitor, an exterior case and the like of the rear case and the like are made of resins in order to reduce weight and costs. In a frequently-travelling working vehicle such as a forklift, a lightweight monitor is required in terms of fuel consumption.
When the resin-made exterior case is used, since the fins for heat radiation have a larger heat resistance than that of a metal material (e.g., aluminium), heat radiation is not so expected even when an area for heat radiation is enlarged by providing the fins. Further, since a display device mounted in a hydraulic excavator provided with a canopy directly influenced by outside environments (exposure to rain, snow, dust and the like) is required to have sealability to ensure predetermined waterproof performance and dust resistance, a vent cannot be provided in the rear case. For this reason, it is necessary to radiate the inside heat through the outer surface of the exterior case by increasing a surface area of the outer surface.